In the field of manufacturing flat-panel displays such as a thin-film transistor-liquid crystal display (TFT-LCD), a plasma display panel (PDP), an organic electroluminescence (OEL) and the like, a panel is produced through the use of a glass substrate and electrode pads and, in the final test stage of a cell process, the entire electrode pads of a data/gate line are brought into simultaneous contact with a probe card or a probe unit at a probing station. Electric signals are then applied to the electrode pads of the data/gate line through the probe card to thereby test the electrical property thereof, which is referred to as a visual test.
Turning to semiconductor chips, they are manufactured through a number of steps, including steps of producing a wafer, inspecting the wafer and packaging a die. The wafer inspecting step is carried out by what is called an electrical die sorting inspection that tests the semiconductor chips for their electrical property. In the electrical die sorting inspection, a probe card is brought into direct contact with electrode pads of each of the semiconductor chips at a probing station, after which electrical signals are applied to the electrode pads to conduct the electrical property test. Depending on the test results, the semiconductor chips are sorted into qualified products and defective products.
As an example of prior art probing tools, a probe card is composed of an array of small-sized metal needle probes. The needle probes are caused to make contact with electrode pads of a target test object, e.g., a panel of flat-panel displays or a semiconductor chip. Subsequently, electrical signals are applied to through the needle probes to test the electrical connection of the electrode pads.
With the needle type probe card known in the art, each of the metal needle probes can make contact with the corresponding electrode pad at a contact point of reduced size and hence the probe card may be advantageously employed in testing objects with high density electrode pads. However, due largely to the fact that the needle probes are of cantilever type, the smaller the diameter of the individual probes, the weaker the force by which the probes can be pressed against the electrode pads. This involves a problem in that no stable contact can be maintained between the probes and the electrode pads. Another problem posed by the needle type probe card is that, if the narrowly spaced-apart probes are subject to flexural deformation, a short-circuit may arise between the probes thus causing a fatal damage to the electric circuits of the object tested.
Moreover, the task of uniformly aligning the individual probes in the process of producing the prior art probe card has heretofore been performed by manual operations of a worker, which reduces the productivity and the degree of precision of the products.
In recent years, a need exists to form solder balls on a semiconductor chip in advance of conducting a test. During the course of testing the semiconductor chip with solder balls, however, the probes tend to be slipped from the solder balls, thus making it difficult to conduct the test and shortening the life span of the probes.
As another example of the prior art probing tools, a probe card has been proposed of the type comprising an insulating sheet and a plurality of elongated leads disposed on the insulating sheet. A metallic material is plated and built up on the insulating sheet in an effort to miniaturize the pitch of the leads. Attached to one side of the insulating sheet is a holder from which terminals of the insulating sheet and rear terminals of the leads extend. The leads have front terminals which are flexurally deformed under pressure to make contact with electrode pads of a semiconductor chip in a resiliently yieldable manner.
The lead type probe card is disadvantageous in that the leads are unevenly built up by plating and therefore have no uniform thickness, thereby resulting in poor contact between the leads of the probe card and the electrode pads of an object tested. In addition, the leads are bonded to the insulating sheet in a small area, as a result of which the front terminals of the leads may be separated from the insulating sheet when the insulating sheet and the leads are subject to repeated flexural deformation.
As a further example of the prior art probing tools, there has been proposed a probe card that is provided with blade-type probes. The blade-type probes are fabricated by forming slits in an insulator made of, e.g., ceramics, and fitting tips into the slits. The task of fitting the tips is conducted manually by a worker, which is disadvantageous in terms of the productivity and the production costs. Furthermore, the probes of this type are cumbersome and inconvenient to change.